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Definitions & Terms

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RSS - Rich Site Summary:


  • R/3 is the comprehensive set of integrated business applications from Systems, Application and Products in Data Processing , the German company that states it is the market and technology leader in business application software. R/3 replaced an earlier system, R/2, which is still in use. R/3 uses the client-server model and provides the ability to store, retrieve, analyze, and process in many ways corporate data for financial analysis, production operation, human resource management, and most other business processes.
  • A recent release, R/3 3.1, makes it possible to get to the R/3 database and applications through Internet access and Web browsers. A sales representative can initiate the workflow for a sales order by filling out an electronic form on a laptop that will be "translated" into input for the R/3 system. Other interfaces such as Lotus Notes can also be used. The Web implementation adheres to the Workflow Client API standard of the Workflow Management Coalition (WfMC). A more recent version of R/3 adds features designed to speed product delivery by helping to manage the supply chain.

RAD - Rapid Application Development:

  • See Rapid Application Development.

RADIUS - Remote Authentication Dial-In User Service:

  • Remote Authentication Dial-In User Service (RADIUS) is a client/server protocol and software that enables remote access servers to communicate with a central server to authenticate dial-in users and authorize their access to the requested system or service. RADIUS allows a company to maintain user profiles in a central database that all remote servers can share. It provides better security, allowing a company to set up a policy that can be applied at a single administered network point. Having a central service also means that it's easier to track usage for billing and for keeping network statistics. Created by Livingston (now owned by Lucent), RADIUS is a de facto industry standard used by Ascend and other network product companies and is a proposed IETF standard.

RAID - Redundant Array of Independent Disks:

  • See Redundant Array of Independent Disks.


  • RAMAC (pronounced RAY-mac; IBM does not spell out the initials) is a multiple-disk storage subsystem from IBM that emphasizes fault-tolerance and is intended for large enterprises. IBM claims that its RAMAC product family "provides the highest data availability of any DASD subsytem." The RAMAC product family uses redundant array of independent disks technology (RAID ) - in particular, the RAID-5 storage technique. RAMAC also includes redundant (backup) power and cooling subsystems. RAMAC also uses multilevel caching to improve performance and it uses predictive failure analysis to identify potential disk failures.
  • The RAMAC subsystem can be addressed by any operating system (such as IBM's OS/390) that currently works with IBM's main storage controller products. RAMAC is scalable from nine gigabytes up to 90 gigabytes of storage.

RAMAC - original:

  • RAMAC (which stood for random access method of accounting and control) was the world's first computer disk storage system, developed by IBM engineers in San Jose and introduced in 1957. Prior to this, computer storage was largely reliant on magnetic tape . The disk-based storage introduced moveable read/write heads, which enabled a semi-random access capability; this ability was a momentous achievement, both for IBM and for the computing world in general, because fast random access to large volumes of data now made it practical to have interactive computer systems. RAMAC's development also led to IBM opening its first storage manufacturing plant.
  • As part of the IBM 350, RAMAC was a system that used fifty metallic disks, each two feet in diameter, arranged on a rotating spindle. Data was recorded on both sides of the disks, each holding a hundred concentric tracks, for a storage capacity of 5 megabyte s. An access arm under servo control moved two read/write heads to access to any of the tracks. Originally, RAMAC's purchase price worked out to about $10,000 per megabyte of storage capacity; by 1997 the price per megabyte had dropped to about ten cents.

Rapid Application Development - RAD:

  • Rapid Application Development (RAD) is a concept that products can be developed faster and of higher quality through:
  • * Gathering requirements using workshops or focus groups
  • * Prototyping and early, reiterative user testing of designs
  • * The re-use of software components
  • * A rigidly paced schedule that defers design improvements to the next product version
  • * Less formality in reviews and other team communication
  • Some companies offer products that provide some or all of the tools for RAD software development. (The concept can be applied to hardware development as well.) These products include requirements gathering tools, prototyping tools, computer-aided software engineering tools, language development environments such as those for the Java platform, groupware for communication among development members, and testing tools. RAD usually embraces object-oriented programming methodology, which inherently fosters software re-use. The most popular object-oriented programming languages, C++ and Java, are offered in visual programming packages often described as providing rapid application development.

RARP - Reverse Address Resolution Protocol:

  • See Reverse Address Resolution Protocol.

Rational Number:

  • A Rational Number is a number determined by the ratio of some integer p to some nonzero natural number q. The SET of rational numbers is denoted Q, and represents the set of all possible integer-to-natural-number ratios p/q. In mathematical expressions, unknown or unspecified rational numbers are represented by lowercase, italicized letters from the late middle or end of the alphabet, especially r, s, and t, and occasionally u through z. Rational numbers are primarily of interest to theoreticians. Theoretical mathematics has potentially far-reaching applications in communications and computer science, especially in data encryption and security.
  • If r and t are rational numbers such that r < t, then there exists a rational number s such that r < s < t. This is true no matter how small the difference between r and t, as long as the two are not equal. In this sense, the set Q is "dense." Nevertheless, Q is a denumerable set. Denumerability refers to the fact that, even though a set might contain an infinite number of elements, and even though those elements might be "densely packed," the elements can be defined by a list that assigns them each a unique number in a sequence corresponding to the set of natural numbers N = {1, 2, 3, ...}..
  • For the set of natural numbers N and the set of integers Z, neither of which are "dense," denumeration lists are straightforward. For Q, it is less obvious how such a list might be constructed. An example appears below. The matrix includes all possible numbers of the form p/q, where p is an integer and q is a nonzero natural number. Every possible rational number is represented in the array. Following the pink line, think of 0 as the "first stop," 1/1 as the "second stop," -1/1 as the "third stop," 1/2 as the "fourth stop," and so on. This defines a sequential (although redundant) list of the rational numbers. There is a one-to-one correspondence between the elements of the array and the set of natural numbers N.
  • In contrast to the natural numbers, integers, and rational numbers, the sets of irrational numbers, real numbers, imaginary numbers, and complex numbers are non-denumerable. They have cardinality greater than that of the set N. This leads to the conclusion that some "infinities" are larger than others!

RDF - Resource Description Framework:

  • See Resource Description Framework.

RDF Site Summary:

  • RDF Site Summary (RSS) - also referred to as Rich Site Summary - is a method of describing news or other Web content that is available for "feeding" (distribution or syndication) from an online publisher to Web users. RSS is an application of the Extensible Markup Language (XML) that adheres to the World Wide Web Consortium's Resource Description Framework (RDF). Originally developed by Netscape for its browser's Netcenter channels, the RSS specification is now available for anyone to use.
  • A Web site that wants to "publish" some of its content, such as news headlines or stories, creates a description of the content and specifically where the content is on its site in the form of an RSS document. The publishing site then registers its RSS document with one of several existing directories of RSS publishers. A user with a Web browser or a special program that can read RSS-distributed content can read periodically-provided distributions. Some current directories of RSS files include Meerkat, GropSoup, NewsIsFree, UserLand, and XML Tree; these sites are sometimes known as content aggregators. RSS browsers include Headline Viewer and Novobot.
  • News is only one form of content that can be distributed with an RSS feed. Other possibilities include discussion forum excerpts, software announcements, and any form of content retrievable with a URL.

Real Time:

  • Real time is a level of computer responsiveness that a user senses as sufficiently immediate or that enables the computer to keep up with some external process (for example, to present visualizations of the weather as it constantly changes). Real-time is an adjective pertaining to computers or processes that operate in real time. Real time describes a human rather than a machine sense of time.
  • In the days when mainframe batch computers were predominant, an expression for a mainframe that interacted immediately with users working from connected terminals was online in real time.

Real Time Operating System - RTOS:

  • A Real Time Operating System (RTOS) is an operating system that guarantees a certain capability within a specified time constraint. For example, an operating system might be designed to ensure that a certain object was available for a robot on an assembly line. In what is usually called a "hard" real-time operating system, if the calculation could not be performed for making the object available at the designated time, the operating system would terminate with a failure. In a "soft" real-time operating system, the assembly line would continue to function but the production output might be lower as objects failed to appear at their designated time, causing the robot to be temporarily unproductive. Some real-time operating systems are created for a special application and others are more general purpose. Some existing general purpose operating systems claim to be a real-time operating systems. To some extent, almost any general purpose operating system such as Microsoft's Windows 2000 or IBM's OS/390 can be evaluated for its real-time operating system qualities. That is, even if an operating system doesn't qualify, it may have characteristics that enable it to be considered as a solution to a particular real-time application problem.
  • In general, real-time operating systems are said to require:
  • * multitasking
  • * Process threads that can be prioritized
  • * A sufficient number of interrupt levels
  • Real-time operating systems are often required in small embedded operating systems that are packaged as part of microdevices. Some kernels can be considered to meet the requirements of a real-time operating system. However, since other components, such as device drivers, are also usually needed for a particular solution, a real-time operating system is usually larger than just the kernel.

Real Time Transfer Protocol - RTO:

  • Real Time Transfer Protocol (RTP) is an Internet protocol standard that specifies a way for programs to manage the real-time transmission of multimedia data over either unicast or multicast network services. Originally specified in Internet Engineering Task Force (IETF) Request for Comments (RFC) 1889, RTP was designed by the IETF's Audio-Video Transport Working Group to support video conferences with multiple, geographically dispersed participants. RTP is commonly used in Internet telephony applications. RTP does not in itself guarantee real-time delivery of multimedia data (since this is dependent on network characteristics); it does, however, provide the wherewithal to manage the data as it arrives to best effect.
  • RTP combines its data transport with a control protocol (RTCP), which makes it possible to monitor data delivery for large multicast networks. Monitoring allows the receiver to detect if there is any packet loss and to compensate for any delay jitter. Both protocols work independently of the underlying Transport layer and Network layer protocols. Information in the RTP header tells the receiver how to reconstruct the data and describes how the codec bit streams are packetized. As a rule, RTP runs on top of the User Datagram Protocol (UDP), although it can use other transport protocols. Both the Session Initiation Protocol (SIP) and H.323 use RTP.
  • RTP components include: a sequence number, which is used to detect lost packets; payload identification, which describes the specific media encoding so that it can be changed if it has to adapt to a variation in bandwidth; frame indication, which marks the beginning and end of each frame; source identification, which identifies the originator of the frame; and intramedia synchronization, which uses timestamps to detect different delay jitter within a single stream and compensate for it.
  • RTPC components include: quality of service (QoS) feedback , which includes the numbers of lost packets, round-trip time, and jitter, so that the sources can adjust their data rates accordingly; session control, which uses the RTCP BYE packet to allow participants to indicate that they are leaving a session; identification, which includes a participant's name, e-mail address, and telephone number for the information of other participants; and intermedia synchronization, which enables the synchronization of separately transmitted audio and video streams.
  • Compressed RTP (CRTP), specified in RFC 2509, was developed to decrease the size of the IP, UDP, and RTP headers. However, it was designed to work with reliable and fast point-to-point links. In less than optimal circumstances, where there may be long delays, packet loss, and out-of-sequence packets, CRTP doesn't function well for Voice over IP (VoIP ) applications. Another adaptation, Enhanced CRPT (ECRPT), was defined in a subsequent Internet Draft document to overcome that problem.

Red Hat Linux:

  • Red Hat is a leading software company in the business of assembling open source components for the Linux operating system and related programs into a distribution package that can easily be ordered. Red Hat provides over 400 different software packages, including the C language compiler from Cygnus, a Web server from Apache, and the X Window System from X Consortium. The advantages to buying the distribution from Red Hat rather than assembling it at no cost yourself from various sources is that you get it as a single assembled package. Red Hat also offers service that isn't provided as quickly by the individual component developers, including members of the Free Software Foundation . Like all free software, Red Hat's packages allow the buyer to modify and even resell modified versions of code as long as they do not restrict anyone else from further modification.
  • Red Hat was one of the first companies to realize that "free" software could be sold as a product. After examining the successful marketing campaign of Evian water, Red Hat concluded that to achieve success, the company had to create more Linux users and brand Red Hat as the Linux name that customers preferred. Today, the "Red Hat Plan" is discussed as a model in business schools.


  • In information technology, the term redundant has several usages:
  • 1) Redundant describes computer or network system components, such as fans, hard disk drives, servers, operating systems, switches, and telecommunication links that are installed to back up primary resources in case they fail. A well-known example of a redundant system is the redundant array of independent disks (redundant array of independent disks).
  • 2) Redundant information is unneeded or duplicated information.
  • 3) Redundant bits are extra binary digits that are generated and transferred along with a data transfer to ensure that no bits were lost during the data transfer.
  • Redundancy is the quality of a system, an item of information, or a bit that is redundant.

Redundant Array of Independent Disks - RAID:

  • Redundant Array of Independent Disks; originally redundant array of inexpensive disks (RAID) is a way of storing the same data in different places (thus, redundantly) on multiple hard disk s. By placing data on multiple disks, I/O operations can overlap in a balanced way, improving performance. Since multiple disks increases the mean time between failure (MTBF), storing data redundantly also increases fault-tolerance.
  • A RAID appears to the operating system to be a single logical hard disk. RAID employs the technique of striping , which involves partitioning each drive's storage space into units ranging from a sector (512 bytes) up to several megabytes. The stripes of all the disks are interleaved and addressed in order.
  • In a single-user system where large records, such as medical or other scientific images, are stored, the stripes are typically set up to be small (perhaps 512 bytes) so that a single record spans all disks and can be accessed quickly by reading all disks at the same time.
  • In a multi-user system, better performance requires establishing a stripe wide enough to hold the typical or maximum size record. This allows overlapped disk I/O across drives.
  • There are at least nine types of RAID plus a non-redundant array (RAID-0):
  • * RAID-0. This technique has striping but no redundancy of data. It offers the best performance but no fault-tolerance.
  • * RAID-1. This type is also known as disk mirroring and consists of at least two drives that duplicate the storage of data. There is no striping. Read performance is improved since either disk can be read at the same time. Write performance is the same as for single disk storage. RAID-1 provides the best performance and the best fault-tolerance in a multi-user system.
  • * RAID-2. This type uses striping across disks with some disks storing error checking and correcting (ECC) information. It has no advantage over RAID-3.
  • * RAID-3. This type uses striping and dedicates one drive to storing parity information. The embedded error checking (ECC) information is used to detect errors. Data recovery is accomplished by calculating the exclusive OR (XOR) of the information recorded on the other drives. Since an I/O operation addresses all drives at the same time, RAID-3 cannot overlap I/O. For this reason, RAID-3 is best for single-user systems with long record applications.
  • * RAID-4. This type uses large stripes, which means you can read records from any single drive. This allows you to take advantage of overlapped I/O for read operations. Since all write operations have to update the parity drive, no I/O overlapping is possible. RAID-4 offers no advantage over RAID-5.
  • * RAID-5. This type includes a rotating parity array, thus addressing the write limitation in RAID-4. Thus, all read and write operations can be overlapped. RAID-5 stores parity information but not redundant data (but parity information can be used to reconstruct data). RAID-5 requires at least three and usually five disks for the array. It's best for multi-user systems in which performance is not critical or which do few write operations.
  • * RAID-6. This type is similar to RAID-5 but includes a second parity scheme that is distributed across different drives and thus offers extremely high fault- and drive-failure tolerance. There are few or no commercial examples currently.
  • * RAID-7. This type includes a real-time embedded operating system as a controller, caching via a high-speed bus, and other characteristics of a stand-alone computer. One vendor offers this system.
  • * RAID-10. This type offers an array of stripes in which each stripe is a RAID-1 array of drives. This offers higher performance than RAID-1 but at much higher cost.
  • * RAID-53. This type offers an array of stripes in which each stripe is a RAID-3 array of disks. This offers higher performance than RAID-3 but at much higher cost.

Registered Port Numbers:

  • The Registered Port Numbers are the port numbers that companies and other users register with the Internet Corporation for Assigned Names and Numbers (ICANN) for use by the applications that communicate using the Internet's Transmission Control Protocol (TCP) or the User Datagram Protocol (UDP ). In most cases, these applications run as ordinary programs that can be started by nonprivileged users. The registered port numbers are in the range from 1024 through 49151. They follow in sequence the well-known port numbers, which are, in most cases, applications that can only be started by privileged users, such as the Hypertext Transfer Protocol (HTTP) and Post Office Protocol Version 3 (POP3) applications. When one application communicates with another application at another host computer on the Internet, it specifies that application in each data transmission by using its port number.
  • Examples of applications with registered port numbers include Sun's NEO Object Request Broker (port numbers 1047 and 1048) and Shockwave (port number 1626). Besides the well-known port numbers and the registered port numbers, the remaining ports in the port number spectrum are referred to as dynamic ports or private ports and are numbered from 49152 through 65535. Before the arrival of ICANN, the port numbers were administered by the Internet Internet Assigned Numbers Authority (IANA).

Remote Access:

  • Remote Access is the ability to get access to a computer or a network from a remote distance. In corporations, people at branch offices, telecommuters, and people who are travelling may need access to the corporation's network. Home users get access to the Internet through remote access to an Internet service provider (ISP). Dial-up connection through desktop, notebook, or handheld computer modem over regular telephone lines is a common method of remote access. Remote access is also possible using a dedicated line between a computer or a remote local area network and the "central" or main corporate local area network. A dedicated line is more expensive and less flexible but offers faster data rates. Integrated Services Digital Network (ISDN) is a common method of remote access from branch offices since it combines dial-up with faster data rates. wireless, cable modem, and Digital Subscriber Line (DSL) technologies offer other possibilities for remote access.
  • A remote access server is the computer and associated software that is set up to handle users seeking access to network remotely. Sometimes called a communication server, a remote access server usually includes or is associated with a firewall server to ensure security and a router that can forward the remote access request to another part of the corporate network. A remote access server may include or work with a modem pool manager so that a small group of modems can be shared among a large number of intermittently present remote access users. A remote access server may also be used as part of a virtual private network (VPN).

Remote Network Monitoring - RMON:

  • Remote Network Monitoring (RMON) provides standard information that a network administrator can use to monitor, analyze, and troubleshoot a group of distributed local area networks (LANs) and interconnecting T-1/E-1 and T-2/E-3 lines from a central site. RMON specifically defines the information that any network monitoring system will be able to provide. It's specified as part of the Management Information Base (MIB) in Request for Comments 1757 as an extension of the Simple Network Management Protocol (SNMP). The latest level is RMON Version 2 (sometimes referred to as "RMON 2" or "RMON2").
  • RMON can be supported by hardware monitoring devices (known as "probes") or through software or some combination. For example, Cisco's line of LAN switches includes software in each switch that can trap information as traffic flows through and record it in its MIB. A software agent can gather the information for presentation to the network administrator with a graphical user interface. A number of vendors provide products with various kinds of RMON support.
  • RMON collects nine kinds of information, including packets sent, bytes sent, packets dropped, statistics by host, by conversations between two sets of addresses, and certain kinds of events that have occurred. A network administrator can find out how much bandwidth or traffic each user is imposing on the network and what Web sites are being accessed. Alarms can be set in order to be aware of impending problems.

Remote Procedure Call - PRC:

  • Remote Procedure Call (RPC) is a protocol that one program can use to request a service from a program located in another computer in a network without having to understand network details. (A procedure call is also sometimes known as a function call or a subroutine call.) RPC uses the client/server model. The requesting program is a client and the service-providing program is the server. Like a regular or local procedure call, an RPC is a synchronous operation requiring the requesting program to be suspended until the results of the remote procedure are returned. However, the use of lightweight processes or threads that share the same address space allows multiple RPCs to be performed concurrently.
  • When program statements that use RPC are compiled into an executable program, a stub is included in the compiled code that acts as the representative of the remote procedure code. When the program is run and the procedure call is issued, the stub receives the request and forwards it to a client runtime program in the local computer. The client runtime program has the knowledge of how to address the remote computer and server application and sends the message across the network that requests the remote procedure. Similarly, the server includes a runtime program and stub that interface with the remote procedure itself. Results are returned the same way.
  • There are several RPC models and implementations. A popular model and implementation is the Open Software Foundation's Distributed Computing Environment (DCE). The Institute of Electrical and Electronics Engineers defines RPC in its ISO Remote Procedure Call Specification, ISO/IEC CD 11578 N6561, ISO/IEC, November 1991.
  • RPC spans the Transport layer and the Application layer in the Open Systems Interconnection (OSI ) model of network communication. RPC makes it easier to develop an application that includes multiple programs distributed in a network. Alternative methods for client/server communication include message queueing and IBM's Advanced Program-to-Program Communication (APPC).

Resource Description Framework - RDF:

  • Resource Description Framework (RDF) is a general framework for how to describe any Internet resource such as a Web site and its content. An RDF description (such descriptions are often referred to as metadata , or "data about data") can include the authors of the resource, date of creation or updating, the organization of the pages on a site (the sitemap), information that describes content in terms of audience or content rating, key words for search engine data collection, subject categories, and so forth. The Resource Description Framework will make it possible for everyone to share Web site and other descriptions more easily and for software developers to build products that can use the metadata to provide better search engines and directories, to act as intelligent agents, and to give Web users more control of what they're viewing. The RDF is an application of another technology, the Extensible Markup Language (XML), and is being developed under the auspices of the World Wide Consortium (W3C).
  • A certain amount of metadata is already provided for Web site resources using the Hypertext Markup Language (HTML ). For example, when we wrote this page, we added HTML statements containing key words that describe the content of this definition and that are used by search engines for indexing. We also added a one-sentence description that can be shown by search engines. (These statements, called META tag statements, are invisible to you unless you click on this page and then right-click on "View source"). Less formally, the "Created on" or "Updated on" date at the bottom of this definition is also metadata - that is, data that tells you something about the data or content on this page. These are simply a few examples of many possible existing and future resource descriptions needed about a Web resource.
  • Originally conceived as an extension of the content rating PICS Recommendation, the RDF will in time subsume it, with the idea that it can express any data that a PICS-1.1 label can express. However, both RDF and the equivalent PICS expression are expected to be in use for a while.
  • Here are some of the likely benefits:
  • * By providing a consistent framework, RDF will encourage the providing of metadata about Internet resources.
  • * Because RDF will include a standard syntax for describing and querying data, software that exploits metadata will be easier and faster to produce.
  • * The standard syntax and query capability will allow applications to exchange information more easily.
  • * Searchers will get more precise results from searching, based on metadata rather than on indexes derived from full text gathering.
  • * Intelligent software agents will have more precise data to work with.
  • How RDF Works
  • An Internet resource is defined as any resource with a Uniform Resource Identifier (URI). This includes the Uniform Resource Locators (URL) that identify entire Web sites as well as specific Web pages. As with today's HTML META tags, the RDF description statements, encased as part of an Extensible Markup Language (XML) section, could be included within a Web page (that is, a Hypertext Markup Language - HTML - file) or could be in separate files.
  • RDF is now a formal W3C Recommendation, meaning that it is ready for general use. Currently, a second W3C recommendation, still at the Proposal stage, proposes a system in which the descriptions related to a particular purpose (for example, all descriptions related to security and privacy) would constitute a class of such like descriptions (using class here much as it is used in object-oriented programming data modeling and programming). Such classes could fit into a schema or hierarchy of classes, with subclasses of a class able to inherit the descriptions of the entire class. The schema of classes proposal would save having to repeat descriptions since a single reference to the class of which a particular RDF description was a part would suffice. The scheme or description of the collection of classes could itself be written in RDF language.

Reverse Address Resolution Protocol - RARP:

  • Reverse Address Resolution Protocol (RARP) is a protocol by which a physical machine in a local area network can request to learn its IP address from a gateway server's Address Resolution Protocol (ARP) table or cache. A network administrator creates a table in a local area network's gateway router that maps the physical machine (or Media Access Control - MAC address) addresses to corresponding Internet Protocol addresses. When a new machine is set up, its RARP client program requests from the RARP server on the router to be sent its IP address. Assuming that an entry has been set up in the router table, the RARP server will return the IP address to the machine which can store it for future use. RARP is available for Ethernet, Fiber Distributed-Data Interface, and token ring LANs.

RIP - Routing Information Protocol:

  • See Routing Information Protocol.


  • See Telephone Jacks.


  • Rlogin (remote login) is a UNIX command that allows an authorized user to login to other UNIX machines (host s) on a network and to interact as if the user were physically at the host computer. Once logged in to the host, the user can do anything that the host has given permission for, such as read, edit, or delete files.
  • Rlogin is similar to the better known Telnet command. Rlogin is considered useful for simple logins that don't require a lot of control over the client/host interaction, but is thought to be less useful than Telnet where a lot of customization is desired, for multiple sessions, for connections between very distant terminals or to terminals that are not running UNIX, for that matter, since rlogin can only connect to UNIX hosts. A benefit of rlogin is the ability to use a file called .rhosts that resides on the host machine and maintains a list of terminals allowed to login without a password. A secure version of rlogin (slogin) was combined with two other UNIX utility, ssh and scp, in the Secure Shell suite, an interface and protocol created to replace the earlier utilities.

RMON - Remote Network Monitoring:

  • ee Remote Network Monitoring.


  • RNIS (Reseau Numerique a Integration de Services) is the European name for Integrated Services Digital Network (ISDN). See our definition of Integrated Services Digital Network (ISDN).

Roaming Service:

  • Roaming Service is the ability to get access to the Internet when away from home at the price of a local call or at a charge considerably less than the regular long-distance charges. For example, if you normally get access to the Internet from an access provider in Brooklyn, New York and are travelling to Hong Kong, you can call a designated access provider in Hong Kong. Instead of paying long distance charges to your local provider in Brooklyn, you pay the local phone connection charge in Hong Kong and possibly a modest additional charge for the service.
  • Roaming service is made possible through Internet service providers (ISP s) who have cooperative agreements to grant each others' customers local access to the Internet. Special software allows cooperating ISPs to keep track of and calculate prearranged payments for usage differences. Here's how it works for the user:
  • 1. The Internet user must already subscribe to an ISP that offers roaming service arrangements.
  • 2. Assuming the ISP does, the user can determine a cooperating ISP in a city to which the user is travelling.
  • 3. In the travel location, the user can call the local ISP's designated phone number through the computer modem, entering information during login that will identify the user's home ISP.
  • 4. The "foreign" ISP will contact the ISP and determine that the user is a valid user.
  • 5. The "foreign" ISP will grant the user access to the Internet. The user will be able to access e-mail from the home mail server.
  • 6. The user will be charged at local phone rates. In addition, depending on the particular service arrangement, the home ISP may levy an additional hourly usage charge of several dollars an hour or a monthly charge in case the service is used during that month.
  • A similar roaming service is provided by some cooperating cellular telephone telephone or personal digital assistant (PDA) service providers.
  • If you are travelling and simply need to be able to exchange e-mail, you can consider getting a freemail membership (usually free) from HotMail, Rocketmail, or other freemail providers. Hotmail also offers POP3 server accounts for access to up to four e-mail accounts you may already have, assuming you remember the POP3 server name and your user IDs and passwords.
  • If you subscribe to a somewhat global service such as AT&T's WorldNet or the IBM Global Network, you may already be able to access your account in certain cities through your provider's local point-of-presence (POP) on the Internet without having to pay for a long-distance call.


  • See Spiders.

ROLAP - Relational Online Analytical Processing:

  • Relational online analytical processing (ROLAP) is a form of online analytical processing (OLAP) that performs dynamic multidimensional analysis of data stored in a relational database rather than in a multidimensional database (which is usually considered the OLAP standard).
  • Data processing may take place within the database system, a mid-tier server, or the client. In a two-tiered architecture, the user submits a Structure Query Language (SQL ) query to the database and receives back the requested data. In a three-tiered architecture, the user submits a request for multidimensional analysis and the ROLAP engine converts the request to SQL for submission to the database. Then the operation is performed in reverse: the engine converts the resulting data from SQL to a multidimensional format before it is returned to the client for viewing. As is typical of relational databases, some queries are created and stored in advance. If the desired information is available, then that query will be used, which saves time. Otherwise, the query is created on the fly from the user request. Microsoft Access's PivotTable is an example of a three-tiered architecture.
  • Since ROLAP uses a relational database, it requires more processing time and/or disk space to perform some of the tasks that multidimensional databases are designed for. However, ROLAP supports larger user groups and greater amounts of data and is often used when these capacities are crucial, such as in a large and complex department of an enterprise.

Root Directory - Login as Root:

  • In a computer file system that is organized as a hierarchy or tree, the Root Directory is the directory that includes all other directories. (Unlike a real tree, a tree file system has only one root!) In UNIX-based as well as in other operating system , the root directory has no name. It is simply represented by the special character that separates directories in a file system.
  • In UNIX-based systems, the root directory is represented simply as:
  • /
  • In Windows systems, the root directory is represented as:
  • \
  • Only a few special users of a shared operating system will be given the authority to access all file directories and files under the root directory.

Root Server System

  • On the Internet, the Root Server System is the way that an authoritative master list of all top-level domain name (such as com, net, org , and individual country codes) is maintained and made available. The system consists of 13 file servers. The central or "A" server is operated by Network Solutions, Inc., the company that currently manages domain name registration, and the master list of top-level domain (TLD) names is kept on the A server. On a daily basis, this list is replicated to 12 other geographically dispersed file servers that are maintained by an assortment of agencies. The Internet routing system uses the nearest root server list to update routing tables.


  • RosettaNet is an organization set up by leading information technology companies to define and implement a common set of standards for e-business . RosettaNet is defining a common parts dictionary so that different companies can define the same product the same way. It is also defining up to 100 e-business transaction processes and standardizing them. Because RosettaNet is supported by all or most of the major companies in the IT industry, its standards are expected to be widely adopted.
  • RosettaNet has developed a structured four-part approach for creating what it calls Partner Interface Processes (PIPs).
  • * Business Process Modeling examines common business procedures and defines the components of the processes.
  • * Business Process Analysis analyzes the processes and defines a target list of desireable changes to the processes.
  • * PIP Development establishes guidelines and documentation for the changes.
  • * Dictionaries consist of two data dictionary : a technical properties dictionary and a business properties dictionary. Along with the RosettaNet Implementation Framework (which defines an exchange protocol for PIP implementation), the dictionaries form the basis for PIP development.
  • RosettaNet's more than 40 members include Microsoft, Netscape, 3Com, Toshiba America, Compaq, CompUSA, Hewlett-Packard, IBM, and Intel. Its name refers to the Rosetta Stone, a stone on which Egyptian hieroglyphics were also written in other languages, making it possible to decipher the hieroglyphics. Rosetta stone has the more general meaning of "something that provides a key to understanding." The organization's slogan is "lingua franca for eBusiness." (A lingua franca is a common second language, such as English for countries in the industrialized world whose first language is not English.)


  • ROT-13 is the encrypting of a message by exchanging each of the letters on the first half of the alphabet with the corresponding letter in the second half of the alphabet (that is, swapping positions by 13 characters). Thus, A becomes N, B becomes O, and so forth, and conversely, N becomes A, O becomes B, and so forth. Numbers, spaces and punctuation are not changed. ROT-13 is sometimes used to encrypt messages that may be offensive or of questionable taste, or messages that contain spoilers (like movie endings or punch lines). The purpose of the code is not to guarantee security, but simply to make it difficult for anyone to read.
  • ROT-13 is sometimes used on the Internet to encrypt e-mail addresses to discourage spamming. Some browsers or Word editors offer users the ability to convert back and forth between regular text and ROT-13. Typically, you highlight text you want to encrypt or decrypt and then select the ROT-13 encode/decode button.
  • Here's an example of some regular text:
  • This is a sample of a message encoded using ROT-13 encoding. Because of the simple nature of the encryption, its purpose is not security but to prevent accidental reading.
  • that would look like this in ROT-13:
  • Guvf vf n fnzcyr bs n zrffntr rapbqrq hfvat EBG-13 rapbqvat. Orpnhfr bs gur fvzcyr angher bs gur rapelcgvba, vgf checbfr vf abg frphevgl ohg gb cerirag nppvqragny ernqvat.
  • ROT-13 is sometimes known as Caesar's code because the Romans General is said to have used it during the Pelloponesian Wars.


  • On the Internet, a Router is a device or, in some cases, software in a computer, that determines the next network point to which a packet should be forwarded toward its destination. The router is connected to at least two networks and decides which way to send each information packet based on its current understanding of the state of the networks it is connected to. A router is located at any gateway (where one network meets another), including each Internet point-of-presence. A router is often included as part of a network switch.
  • A router may create or maintain a table of the available routes and their conditions and use this information along with distance and cost algorithms to determine the best route for a given packet. Typically, a packet may travel through a number of network points with routers before arriving at its destination. Routing is a function associated with the Network layer (layer 3) in the standard model of network programming, the Open Systems Interconnection (OSI) model. A layer-3 switch is a switch that can perform routing functions.
  • An edge router is a router that interfaces with an asynchronous transfer mode (ATM) network. A brouter is a network bridge combined with a router.

Routing Information Protocol - RIP:

  • Routing Information Protocol (RIP) is a widely-used protocol for managing router information within a self-contained network such as a corporate local area network or an interconnected group of such LANs. RIP is classified by the Internet Engineering Task Force (IETF) as one of several internal gateway protocols (Interior Gateway Protocol).
  • Using RIP, a gateway host (with a router) sends its entire routing table (which lists all the other hosts it knows about) to its closest neighbor host every 30 seconds. The neighbor host in turn will pass the information on to its next neighbor and so on until all hosts within the network have the same knowledge of routing paths, a state known as network convergence. RIP uses a hop count as a way to determine network distance. (Other protocols use more sophisticated algorithms that include timing as well.) Each host with a router in the network uses the routing table information to determine the next host to route a packet to for a specified destination.
  • RIP is considered an effective solution for small homogeneous networks. For larger, more complicated networks, RIP's transmission of the entire routing table every 30 seconds may put a heavy amount of extra traffic in the network. The major alternative to RIP is the Open Shortest Path First Protocol (OSPF).

Routing Switch:

  • In a network, a Routing Switch is a device that combines the functions of a switch, which forwards data by looking at a physical device address, and a router, which forwards packets by locating a next hop address.

Roving Analysis Port:

  • See Port Mirroring.

RPC - Remote Procedure Call:

  • See Remote Procedure Call.


  • RSA is an Internet encryption and authentication system that uses an algorithm developed in 1977 by Ron Rivest, Adi Shamir, and Leonard Adleman. The RSA algorithm is the most commonly used encryption and authentication algorithm and is included as part of the Web browsers from Microsoft and Netscape. It's also part of Lotus Notes , Intuit's Quicken, and many other products. The encryption system is owned by RSA Security. The company licenses the algorithm technologies and also sells development kits. The technologies are part of existing or proposed Web, Internet, and computing standards.
  • How the RSA System Works
  • The mathematical details of the algorithm used in obtaining the public and private keys are available at the RSA Web site. Briefly, the algorithm involves multiplying two large prime numbers (a prime number is a number divisible only by that number and 1) and through additional operations deriving a set of two numbers that constitutes the public key and another set that is the private key . Once the keys have been developed, the original prime numbers are no longer important and can be discarded. Both the public and the private keys are needed for encryption /decryption but only the owner of a private key ever needs to know it. Using the RSA system, the private key never needs to be sent across the Internet.
  • The private key is used to decrypt text that has been encrypted with the public key. Thus, if I send you a message, I can find out your public key (but not your private key) from a central administrator and encrypt a message to you using your public key. When you receive it, you decrypt it with your private key. In addition to encrypting messages (which ensures privacy), you can authenticate yourself to me (so I know that it is really you who sent the message) by using your private key to encrypt a digital certificate. When I receive it, I can use your public key to decrypt it.

RSS - Rich Site Summary:

  • See RDF Site Summary.


RSVP - Resource Reservation Protocol:

  • Resource Reservation Protocol (RSVP) is a set of communication rules that allows channels or paths on the Internet to be reserved for the multicast (one source to many receivers) transmission of video and other high-bandwidth messages. RSVP is part of the Internet Integrated Service (IIS) model, which ensures best-effort service, real-time service, and controlled link-sharing.
  • The basic routing philosophy on the Internet is "best effort," which serves most users well enough but isn't adequate for the continuous stream transmission required for video and audio programs over the Internet. With RSVP, people who want to receive a particular Internet "program" (think of a television program broadcast over the Internet) can reserve bandwidth through the Internet in advance of the program and be able to receive it at a higher data rate and in a more dependable data flow than usual. When the program starts, it will be multicast to those specific users who have reserved routing priority in advance. RSVP also supports unicast (one source to one destination) and multi-source to one destination transmissions.
  • How It Works
  • Let's assume that a particular video program is to be multicast at a certain time on Monday evening. Expecting to receive it, you send an RSVP request before the broadcast (you'll need a special client program or perhaps your browser includes one) to allocate sufficient bandwidth and priority of packet scheduling for the program. This request will go to your nearest Internet gateway with an RSVP server. It will determine whether you are eligible to have such a reservation set up and, if so, whether sufficient bandwidth remains to be reserved to you without affecting earlier reservations. Assuming you can make the reservation and it is entered, the gateway then forwards your reservation to the next gateway toward the destination (or source of multicast). In this manner, your reservation is ensured all the way to the destination. (If the reservation can't be made all the way to the destination, all reservations are removed.)
  • When the multicast begins, packets from the source speed through the Internet on a high-priority basis. As packets arrive at a gateway host, they are classified and scheduled out using a set of queue s and, in some cases, timers. An RSVP packet is very flexible; it can vary in size and in the number of data types and objects. Where packets need to travel through gateways that don't support RSVP, they can be "tunneled" through as ordinary packets. RSVP works with both Internet Protocol version 4 and IPv6.
  • See RDF Site Summary.

RTC - Real Time Clock:

  • A Real Time Clock (RTC) is a battery-powered clock that is included in a microchip in a computer motherboard. This microchip is usually separate from the microprocessor and other chips and is often referred to simply as "the CMOS" (complementary metal-oxide semiconductor). A small memory on this microchip stores system description or setup values - including current time values stored by the real-time clock. The time values are for the year, month, date, hours, minutes, and seconds. When the computer is turned on, the Basic Input-Output Operating System (BIOS) that is stored in the computer's read-only memory (ROM) microchip reads the current time from the memory in the chip with the real-time clock.

RTOS - Real Time Operating System:

  • See Real Time Operating System.

RTO - Real Time Transfer Protocol:

  • See Real Time Transfer Protocol.


  • Ruby is an open source, interpreted, object-oriented programming language created by Yukihiro Matsumoto, who chose the gemstone's name to suggest "a jewel of a language." Ruby is designed to be simple, complete, extensible, and portable. Developed mostly on Linux, Ruby works across most platforms, such as most UNIX-based platforms, DOS, Windows, Macintosh, BeOS, and OS/2, for example. According to proponents, Ruby's simple syntax (partially inspired by Ada and Eiffel), makes it readable by anyone who is familiar with any modern programming language.
  • Ruby is considered similar to Smalltalk and Perl. The authors of the book Programming Ruby: The Pragmatic Programmer's Guide , David Thomas and Andrew Hunt say that it is fully object-oriented, like Smalltalk, although more conventional to use, and as convenient as Perl, but fully object-oriented, which leads to better structured and easier-to-maintain programs. To be compliant with the principles of Extreme Programming (XP), Ruby allows portions of projects to be written in other languages if they are better suited.
  • Ruby has become extremely popular in Japan; it is sometimes said that, at the moment, although there are a huge number of Ruby programmers, most of them don't speak English. That situation is expected to change, however: Hunt and Thomas predict that Ruby will undergo explosive growth between 2001 and 2002, and overtake Python within four years.

Rule Base:

  • In the context of a computer server acting as a firewall , a Rule Base is a set of rules that govern what is and what is not allowed through the firewall. A rule base can work in one of two ways: it can either explicitly assume that all traffic is allowed unless there is a rule to prevent it, or, more typically, it can assume that no traffic may flow through it unless there is an explicit rule to allow it. Rule bases usually work on a top-down principle in which the first rule in the list is acted upon first, so that traffic allowed by the first rule, will never be judged by the remainder of the rules. Rule bases typically have the format of SOURCE / DESTINATION / SERVICE / ACTION.


  • In networks, a runt is a packet that is too small. For example, the Ethernet protocol requires that each packet be at least 64 bytes long. In Ethernet, which operates on the idea that two parties can attempt to get use of the line at the same time and sometimes do, runts are usually the fragments of packet collisions. Runts can also be the result of bad wiring or electrical interference. Runts are recorded by programs that use the Remote Network Monitoring (RNM) standard information base for network adminstration. RMON calls them "undersize packets". A giant is a packet that's oversize.


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